This project is an enzymological study aimed at determining the chemical mechanism whereby oxygen is activated by enzymes called oxygenases. Oxygenases are found in all aerobic organisms and are important in the biosynthesis, transformation, and degradation of steroids, nucleic acids, catecholamines, collagen, drugs, prostaglandins, lignin, and various foreign compounds. These enzymes are crucial to a majority of life forms. Our aims are to continue the investigation of three different types of oxygenases which we have isolated in homogeneous form: 1) Catechol dioxygenases, including catechol and protocatechuate dioxygenases, which are nonheme iron-containing enzymes important in the degradation of aromatic compounds by soil bacteria. 2) Flavoprotein hydroxylases which include bacterial and yeast enzymes such as para-hydroxybenzoate hydroxylase. 3) Phthalate oxygenase, a multicomponent dioxygenase system which converts an unactivated aromatic compound to a dihydrodiol. This type of oxygenase is very important in environmental control of aromatic compounds, and is poorly understood at present. The proposed study will employ rapid kinetics spectrophotometry, chemical quenching, and other enzymological methods. X-ray crystallography and genetic techniques, including cloning, gene sequencing and mutagenesis, will be used extensively to develop a better understanding of these interesting enzymes. We hope that results from these studies will lead to a better understanding of how molecular oxygen is activated for controlled metabolic processes. This in turn may lead to the ability to predict how various compounds will be metabolized in the environment.